Since receptors for transplantation antigens may be visualized directly on unsensitized cells with the use of anti-idiotypic antisera, it should be possible to bind the cells to a cellular immunoabsorbent bearing the appropriate antigens. The cellular immunoabsorbents were monolayers of normal spleen cell attached to polystyrene coated with poly-L lysine. An in vitro murine model of cellular immunity involving generation of cytotoxic cells in mixed lymphocyte culture and assay using Cr15-labelled spleen cells as targets was used. Appropriate monolayers reduced cytotoxic activity of sensitized populations by a median of 94% but were unable to reduce the capacity for sensitization of normal cells or cells past the peak of primary immunization. On the contrary, absorption of these populations usually resulted in nonspecific augmentation up to 100 fold in the ultimate cytotoxic activity.